Electrolytic production of succinic acid from butyrolactone



May 20, 1947. ISHAM 2,420,954

ELECTROLYTIC PRODUCTION OF SUCCINIC ACID FROM BUTYROLACTONE Filed June 12, 1941 Patented May 20, 194'? ELECTROLYTIC PRODUCTION OF succntlo ACID FROM nu'rmomcroun Robert M. Isham, Okmulgee, Okla, assignor to Danciger Oil & Refineries, Inc., Fort Worth; Tex, a corporation of Texas Application June 12, 1941, Serial No. 397,809

1 Claim. (cl. 204-19) E v This invention relates to the production of dibasic acids from corresponding lactones, more particularly to the production of succinic acid from butyrolactone.

In recent .years the demand for succinic acid and its derivatives has markedly increased; In

addition toits employment in the medicinal field,

succinic acid is of importance in synthetic resin manufacture. This acid can be reacted with glycol, for example, 'to produce alkyd resins. Addiin utilizing a simple cell for the electrolysis of a tionally it may be utilized as a catalyst or a modifier for phenol-aldehyde condensation products. Certain of its derivatives, as for example succinic glyceride, .serve as effective plasticizers for the almd type of resins.

The present invention relates to a simple and emcacious method of producing succinic acid from a readily available source material, namely butyrolactone, which may be extracted from pyrollgneous acid residues.

cinic acid readily separated from the solution and or sulphuric acid.

It is known that among the general methodsof formation, succinic acid may be produced by the oxidation of butyrolactone. In the past this has been effected by the utilization of chemical oxidizing agents, such as the chromates and permanganatcs. Such a method of production is quite diillcult by reason of the considerable solubility of succinic acid in water. This solubility necessitates the employment of expensive extraction methods for the recovery of the succinic acid from the resulting reaction mixtures.

As a result of considerable experimentation it has been determined that butyrolactone may be converted to succinic acid electrolytically. As

be seen, such a process presents marked advantages in that it enables the continuous production of succinic acid in high yields and utilizing simplified equipment. In order to enable a more ready comprehension of the invention there is shown in the single figure of the accompanying drawing, in diagrammatic form, a system in which it may be efiectuated;

In the course of investigations from which the present invention eventuated it was ascertained that neither butyrolactone nor succinic acid is reduced by the hydrogen evolved at the cathode of an electrolytic cell where such cathode consisted of the common electrode materials, such as graphite. copper, lead and platinum. It is thus apparent that high yields of the acid are obtainable.

It was further determined that while a diaphragm cell may be used not only is this unao ture of the anode materials.

formed succinic acid from the liquor removed as for example in a filter or preferably a conso is employed is preferably neutral or acid in char- 'varied; excellent results have been obtained by necessary but it is not as effective as a simple so employing sulphuric tends to become concentrated in the anode com- 2 r electrolytic cell.' This is due to the fact that in the diaphragm cell the anion of the electrolyte partment. This necessitates an intermittent or continuous withdrawal of the contents of this compartment, the separation of the contained succinic acid and the return of the unoxidized butyrolactone to the cell. The preferred operation, therefore, is eminently simple and consists solution of butyrolactone containing an added. electrolyte to produce high yields of succinic acid. As will be seen hereinafter, the cell may be Operated intermittently 0r continuously, the suca substantially quantitative conversion secured.

Any suitable electrolyte may be employed and such electrolyte preferably is neutral or acid in character, such for example as sodiumsulphate Essentially the process comprises establishing a conductive solution of butyrolactone as an anolyte and utilizing this as a depolarizer, in an electrolytic cell, to absorb and react with evolved oxygen. As will be appreciated by those skilled in the art, the amount of oxidation is a function of the concentration of the butyrolactone, its

diffusion, the current density at the anode, the temperature of the electrolytic bath and the na- In the present process it is desirable to operate at quite elevated temperatures. Succlnic acid displays a marked increase in solubility in water 'with increase in temperature. For example, at C., 6.8 grams of the acid are dissolved in 100 cc. of water whereas at 100 C., 121 grams dissolve in 100 cc. of water. This rapid increase in solubility with elevated temperatures is happily utilized in the present method to separate the from the cell. By operating the cell at elevated temperatures and by chilling the treated liquor the succinic acid is crystallized and the crystals which form are readily separated from the liquor,

tinuous centrifuge. For these reasons, as noted, it is preferable to maintain the electrolyte at elevated temperatures and it is preferred to operate at about between 40 C. to :C. or higher.

As noted above, the conductive electrolyte which acter. The concentration of the electrolyte in the aqueous solution may be relatively widely acid in concentrations of r As will be appreciated, the process may becarried out in a variety of specifically vdiilerent apparatus of which that shown in the drawings is illustrative. In a typical. embodiment of the invention the initial charge may be made up in the mixing tank I. Such tank is provided with any suitable stirring or agitating mechanism 2. The butyrolactone which is to be treated is fed to the tank in controlled amounts through the line 3 and the make-up water. containing the electrolyte. such as sulphuric acid, is fed through the line 4. As noted previously the amounts fed to the tank are controlled so as to insure an ultimate solution containing between about 20% and 50% o! butyrolactone and fromabout 5% to of sulphuric acid.

The mixing tank is connected to the electrolytic cell 5 by means of the line i which is controlled by valve I. Preferably the line 8 discharges into a weir-box I from which the charging solution overflows into the cell.

Preferably, as shown, the cell is of an elongated type so as to insure the desired prolonged contact of the electrolyte with the anode to insure complete oxidation. In the preferred embodiment the bottom section 9 of the cell serves as the anode and may be constructed of lead, graphite or other conductive and acid resistant material. The elongated cell is provided with the centrally positioned elongated cathode III which may be constructed oi copper, graphite, platinum or other suitable material. The cathshape and may be in the form of a perforated plate, a wire mesh and the like. The cathode and anode are suitably connected in a direct current circuitas shown.

The cell is provided with the outlet or vent pipe I :I through which the hydrogen which is evolved is withdrawn. The treated solution is withdrawn from the'cell through the line I2 which, as shown, is constructed so as automatically to maintain a desired liquid level in the cell 6.

The overflow pipe I2 communicates with any suitable cooling mechanism This may be of any desired type and is shown as a tank I3 provided with the stirring mechanism I4. The tank may be provided with internal coils through which cooling medium is circulated or with an external cooling jacket or both. As explained, the treated solution is rapidly cooled in this unit so as to efiectcrystallization of the succinic acid produced in cell 5. I

The cooling tank I3 communicates with any suitable means for separating the solid succinic acid crystals from the mother liquor. While this may be efiected in any type of filtering or draining mechanism it is preferred to use accelerated filtration and for this purpose the centrifuge I6 is employed. In this unit the crystallized acid is collected in the basket of the centrifuge and the mother liquor flows through line H, controlled by valve I 8 to the receiving tank III. In the course of the reatment the succinic acid crystals 4 the tank [9. In the event that the quantity of wash water added exceeds thatnecessary to replace the water vaporized and electrolytically decomposed during electrolytic action, the excess quantity of water may be drained oil through line 20, controlled by valve 2i. The liquid accumulating in the liquid tank I9 which comprises an acid aqueous solution containing some small amount of succinic acid may be returned to tank I by means of the line 22 having the interposed pump 23. It is particularly to be noted at this point that in as much as the succinic acid is not reduced in the cathode it is unnecessary to remove the uncrystallized portion from the liquor in receiving tank I9 before recycling to the electrolytic cell.

It will be appreciated that with the described type of apparatus there is provided a cyclic method in which butyrolactone may continuously be converted to succinic acid in substantially quantitative yields. The provision of the rapid cooling of the treated electrolyte insures a removal of succinic acid in solid phase from the mother liquor.

The efficacy of the process will be more particularly appreciated upon a consideration of a typical operation. Utilizing an apparatus of the t p described and operating upon an electrolyte containing 5% of sulphuric acid by volume and of butyrolactone by volume a. quantitative conversion of the butyrolactone to succinic acid was secured, namely 118 parts by weight of succinic acid from 86 parts by weight 01 butyrolactone in the charge. In this operation the current density employed was 2.5 amps. per sq. dm. with a potential drop of 2.4 volts. In these circumstances the cell was operated with a current eiflciency of 96%. During this operation the temperature or the electrolyte in cell 5 was main- 40 tained at 62 C. and the temperature Of the ode may, of course, vary widely in design and in the basket may be washed with a spray of ice water and the wash water may be discharged to 7 It will be appreciated that the described method liquor discharged through line I5 was 4 C. The cell employed for this operation was provided with a copper cathode and a lead anode.

The process, as indicated, is eminently simple. It is found that, in operation, the evolution of hydrogen from the cathode is copious and is evolved so rapidly and continuously that it eiiectively agitates the solution so that no mechanical agitation is necessary. Of course, if desired, mechanical agitation may be used to supplement such gas agitation especially in certain cell de- It is found too that a sumciently elevated temperature may be maintained in the cell by the heat generated by the electrolysis of the solution and the heat of reaction resulting from the oxidation of the butyrolactone. Whenever desirable the desired temperature may be maintained by utilizing heating means, such as immersion heaters, closed heating coils and the like in the cell 5 and/ or. the charging tank I.

It is found that the electrolytic oxidation described is rapid and substantially quantitative. Since neither butyrolactone nor succinic acid are cathodically reduced there are no practical limitations imposed on the percentage of these in the liquor which is recycled. If for any reason it is desired to accelerate the oxidation, suitable catalysts (oxygen carriers) may be employed as addition agents, as for example cerous sulphate may be employed. However, as noted, the action is so rapid and the current efiiciency so high that for efllcient and practical operations such addition agents are unnecessary.

,v trolytic production of the desired acid. FOREIGN PATENTS Iclaim! 10 Number Country Date A method of producing succinic acid from 714,2 1 France Sept 1, 1931 butyrolactone which comprises acidifying an aqueous solution of.butyro1act0ne with sulphuric OTHER REFERENCES acid, heating the solution to a temperature of Electro-Organlc Chemistry, by Brockman, 1926, between about 40 C. and 70 C., electrolyzing 15 pages 11-17 and 50. the solution in contact with an anode of large Richters Organic Chemistry, vol. 1, translated surface area, subsequently chilling the solution by Spielmann, 1922, page 492. to recover therefrom crystals or succinic acid. Chemical Abstracts, vol. 27, 1933, page 5253,

6 is characterized as highly by its simplicity as by its eflectiveness. The apparatus required is NITED STATES PATENTS of the simplest possible form and the method Number Name Date is so free from critical factors as to permit con- 551.361 Browne at Dec. 17, 1895 t n us operation. Thus while a preferred em- 5 789,269 Ems May 9' 1905 bodiment of the invention has been described it 1.709.297 Yabuta Apt 16' 1929 is to be understood that this is given as lllus- 2,130,151

Palfreeman et al. Sept. 13, 1938 trative of the fundamental concept of the elec- ROBERT M. ISHAM.

REFERENCES CITED The following references are of record in the file of this patent: 

